Dark, Dark Corners of Perl:

After tonight's PDX.pm meeting, in the bar, I bet Ovid that I could reimplement his Sub::Signatures by replacing the source filter with subroutine attributes. (Wisely, he believed me.)

A few minutes later, he asked idly if I knew of any reason why Perl couldn't call methods with spaces in their names. Offhand, I couldn't think of anything besides the tokenizer that prevents it, believing that gv.c cares more about null-byte termination than the <code>\w+</code>ness of identifiers. If you can bypass that for symbol installation and method invocation (and that's trivial), you've done it.

I hate to give away the punchline before both frightening people who didn't know such things were possible and stumping a few of the people who know it's possible but don't see the answer right away, so here are my tests. They all pass on my machine and I expect them to run just fine on at least Perl 5.8.0 and newer. (Perl 5.6 probably works, but I expect it to fail on more complicated things.) You don't need any non-core modules besides Attribute::Handlers, and I believe that's in the core in the 5.8.x family.

#!/usr/bin/perl -w

 BEGIN
{
	chdir 't' if -d 't';
	use lib '../lib', '../blib/lib';
}

 use strict;
use Test::More tests => 4;

 my $module = 'Attribute::Scary';
use_ok( $module ) or exit;

 package Hello;

 use strict;
use warnings;

 use Attribute::Scary;

 sub new
{
	my ($class, $name) = @_;
	bless \$name, $class;
}

 sub name :Method
{
	return $$self;
}

 sub greet :Method
{
	return sprintf( "Hello, %s!\n", $self->name() );
}

 package main;

 my $hi = Hello->new( 'Bob' );
is( $hi->greet(), "Hello, Bob!\n",
	':Method attribute should autoadd invocant shift' );

 my $spacey_name  = 'spacey 0';
my $spacey_greet = 'spacey 1';

 is( $hi->$spacey_name(), 'Bob',
	'... also installing first method as "spacey 0"' );
is( $hi->$spacey_greet(), "Hello, Bob!\n",
	'... and second as "spacey 1"' );

There are two tricks in the implementation, one of which is an "eww, evil--and CLEVER!" trick and the other is something either you know about or you don't.